Biopolyester melt behavior by torque rheometry

Processability and Degradability of PHA-Based Composites in Terrestrial Environments

In this work, composites based on poly(3-hydroxybutyrate-3-hydroxyvalerate) (PHB-HV) and waste wood sawdust (SD) fibers, a byproduct of the wood industry, were produced by melt extrusion and characterized in terms of processability, thermal stability, morphology, and mechanical properties in order to discriminate the formulations suitable for injection molding. Given their application in agriculture and/or plant nursery, the biodegradability of the optimized composites was investigated under controlled composting conditions in accordance with standard methods (ASTM D5338-98 and ISO 20200-2004). The optimized PHB-HV/SD composites were used for the production of pots by injection molding and their performance was qualitatively monitored in a plant nursery and underground for 14 months. This study presents a sustainable option of valuation of wood factory residues and lowering the production cost of PHB-HV-based compounds without affecting their mechanical properties, improving their impact resistance and biodegradability rates in terrestrial environments.

Response Surface Methodology Approach for Optimization of Extrusion Process of Production of Poly (Hydroxyl Butyrate-Co-Hydroxyvalerate) /Tapioca Starch Blends

Response surface methodology (RSM) was adopted to investigate the optimum operation conditions to develop the biodegradable pellet and to analyze the effects of extrusion processing variables, including tapioca starch content (30–50 %), xylitol content (45–75 g) and barrel temperature (140–170 °C) on characteristics of the Poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV)-starch composites. Maximum loading and maximum displacement of composites could be improved with a deliberate amount of xylitol as well as with rising barrel temperature. The water absorption reduced by addition of xylitol in comparison to increasing tapioca starch content. Coefficients of determination were higher than 0.85 of the response variables and significant regression models were applied to RSM optimization. Based on the response surface and superimposed plots, the compromised optimization condition obtained by numerical optimization was 39.04 % of tapioca-starch content, 56.99 g of xylitol content and 156.58 °C of barrel temperature.

Preparation and Properties of a Novel Class of Polyhydroxyalkanoate Copolymers†

Polyhydroxyalkanoates (PHAs) are biodegradable aliphatic polyesters, known to be produced by many common microorganisms. Nodax is a recently introduced family of PHA copolymers comprising 3-hydroxybutyrate units and a relatively small amount of other medium chain length 3-hydroxyalkanoate (mcl-3HA) comonomers with side groups of at least three carbon units or more. There are several different grades of copolymers available, depending on the average molecular weight, average mcl-3HA content within the copolymer, and side group chain length of the chosen mcl-3HA unit. PHA copolymers with different mcl-3HA types and contents can be made either by bacterial fermentation or by chemical synthesis. The incorporation of mcl-3HA units into PHAs effectively lowers the crystallinity and T(m) in a manner similar to the effect of alpha-olefins in linear low-density polyethylene. The T(m) can be lowered well below the thermal decomposition temperature of PHAs to make this material much easier to process. The reduced crystallinity provides the ductility and toughness required for many practical applications. The mcl-3HA content regulates the T(m) and crystallinity of copolymer almost independently of the branch size, as long as more than three carbons are present in the side group. On the other hand, the side group chain length of the mcl-3HA has a profound effect on the flexibility of copolymer.

Bio-based polymeric composites comprising wood flour as filler

The increasing effort on development of bio-based polymeric materials in recent years is motivated by the basic concept of meeting the sustainability criteria for industrial development in the third millennium. Within this framework, our research group is currently involved in assessing the potentiality of some agro-industrial overproduction and byproducts in the formulation of eco-compatible bio-based polymeric materials displaying, among others, the propensity to biodegrade under controlled environment conditions. In the present work, beech wood flour (Bwf) composites were prepared from plasticized poly(3-hydroxybutyrate) (PHB). The type of plasticizer [tri(ethylene glycol) bis(2-ethylhexanoate) (TEGB) and poly(ethylene glycol) (PEG200)] and the amount [5 and 20 wt %] were selected as independent variables in a factorial design. Thermal and mechanical properties of 90 wt % PHB composites were investigated. Incorporation of PEG200 was found to compromise thermal stability of PHB as demonstrated by the higher decrease on the onset decomposition temperature (T(d)) and the drop in its average molecular weight (M(w)). The present study underlines the fact that TEGB/PHB/beech wood flour composites can be optimized to obtain new materials for disposable items.